Digital photography has become commonplace. Whether the photography is done with a dedicated still camera, a videocamera, or a smartphone having a camera or video function, the high-level procedure is the same. Optics are employed to focus an image of a scene being photographed on a rectangular photodetector array. On command, the photodetector array captures the image as an array of picture elements, or pixels. The pixels are transferred over a bus to a processor and eventually gets written to memory. Additional images may then be captured using the array.
As consumers are aware, today's cameras and smartphones are offering ever-increasing image resolution, expressed in terms of millions of pixels, or megapixels, ever-increasing contrast (e.g., color) depths and ever-increasing rates at which these high-resolution images can be taken. Increasing resolutions, contrast depths and image rates tax the bandwidth of the bus that is responsible for moving the images to the memory. However, compounding these demands are less-apparent advances in image processing in which multiple images are captured in rapid succession, processed and reassembled to allow images to be taken under low-light conditions, increase image depth-of-field, allow the image plane to be changed after-the-fact or reduce the blurring, often called “shutter shake,” that results from camera movement. These image processing techniques further tax the bus, which must now convey the pixels of each of the multiple images to the memory. Fortunately, buses have, so far, been able to accommodate the ever-increasing bandwidth requirements.